We are still more than a year away from the 2018 election. With both parties still regrouping in the aftermath of 2016, and deeply divided, it is an open question what the major issues, messages and scandals will be. However, there is one thing we can already say with near certainty. The number of seats won by each party's candidates will not track the number of votes they received. In 2018, Democrats will win a much smaller number of House seats than their vote share suggests, up to 28 fewer seats than proportionality, making it plausible that Republicans will continue to control the House even if a majority of the votes cast go to Democratic candidates.